Disk drives, also called disk files, are information storage devices that use a rotatable disk with concentric data tracks containing the information, a head or transducer for reading and/or writing data onto the various tracks, and an actuator connected to a carrier for the head for moving the head to the desired track and maintaining it over the track centerline during read or write operations. There are typically a plurality of disks separated by spacer rings and stacked on a hub that is rotated by a disk drive motor. A housing supports the drive motor and head actuator and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface.
In conventional magnetic recording disk drives, the head carrier is an air-bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed. The slider is maintained next to the disk surface by a suspension that connects the slider to the actuator. The slider flies over the disk surface as a consequence of a balance of the spring force from the suspension and the air pressure generated by the velocity of the rotating disk.
In contrast to conventional air-bearing disk drives, liquid-bearing disk drives have been proposed that use a head carrier that is at least partially supported by a liquid film on the disk. In one type of liquid-bearing disk drive, as described in IBM's pending application, U.S. Ser. No. 264,604, filed Oct. 31, 1988, and published May 9, 1990, as European published application EP 367510, and in U.S. Pat. No. 5,097,368 assigned to Conner Peripherals, a relatively thick, continuously recirculating liquid film is maintained on the disk surface and the head carrier is maintained in continuous contact with the liquid film when the disk is rotating at its normal operating speed. In a variation of the liquid-bearing disk drive, as described in U.S. Pat. No. 4,901,185 assigned to Toshiba and U.S. Pat. No. 5,202,803 assigned to IBM, a combined air and liquid bearing supports the head carrier, which is in contact or partial contact with a relatively thin liquid film on the disk.
In both air-bearing and liquid-bearing disk drives, the most common form of actuator is a rotary actuator that moves the head carriers in a nonlinear, generally arcuate path across the disk surfaces. Typically, there are two head carriers per disk, one for each of the "top" and "bottom" disk surfaces, that are attached to the actuator so that the carriers move in unison on the opposite surfaces of the disk. Because the rotary actuator moves in an arcuate path, the heads are not aligned perpendicular to the data tracks, but are skewed relative to the tracks, the amount of skew varying with the radial position.
In the conventional disk drive, a single inductive read/write head performs both read and write functions on the disk. With this type of single-element head, the skew created by the use of a rotary actuator does not present any special problem of head alignment with the data tracks on the disk. However, recent IBM disk drives use dual-element heads, i.e., an inductive element for writing and a magnetoresistive (MR) element for reading. Because the two elements are spaced from one another in a direction perpendicular to the trailing end of the carrier, a rotary actuator is not able to maintain both elements in simultaneous alignment with the data tracks due to the inherent nonlinear path across the disk surface. To compensate for this, dual-element heads are fabricated with the read and write elements offset from one another in a direction parallel to the trailing end of the carrier, the amount of offset being determined by the average skew of the heads. However, since the misalignment of the two elements due to the skew, as seen from the top surface of the disk, is the mirror image of the misalignment of the elements as seen from the bottom surface of the disk, the head with offset read and write elements associated with the top surface must be the mirror image of the head associated with the bottom surface. The result is that two different types of heads must be fabricated: one for the top surfaces of the disks and the other for the bottom surfaces of the disks. This complicates the head manufacturing process and disk drive assembly process.
What is needed is a rotary actuator disk drive that uses identical dual-element read/write transducers for all disk surfaces and that has both elements effectively aligned with the data tracks.